The hands of patients suffering from rheumatoid or osteoarthritis are often deformed by the disease process. Deterioration of the metacarpophalangeal (MCP) joints may cause loss of range, ulnar drift and subluxation, resulting in pain and partial to total dysfunction of the fingers. These conditions can be treated surgically. Implant arthroplasty of the damaged joints involves the insertion of silicone implants which act as spacers between the bones of the reconstructed joint to maintain their internal alignment. Arthroplasty restores some degree of function to the damaged joints and helps alleviate joint pain.
Arthroplasty is most commonly used to reconstruct the MCP joints of arthritic patients. However, the same techniques may be used to repair the distal and proximal interphalangeal joints of the fingers and thumb. This type of MCP joint arthroplasty was pioneered by Dr. Alfred Swanson in the 1960s. The operation involves excision of the metacarpal heads and reaming of the intramedullary canals. A flexible silicone implant with titanium circumferential grommets is then inserted into the canals. Finally, the ligaments and tendons around the implant are reattached to achieve a balanced joint.
The use of splinting in the post-operative management of MCP joint arthroplasty is imperative to the success of the procedure. During recovery, the reconstructed joints must be supported to prevent stretching of reconstructed tendons and ligaments during tissue regeneration. Accordingly, the support should be firm enough to minimize any lateral movement of the fingers. At the same time, the splint should be dynamic enough to allow movement in the desired plane and range. As part of the post-operative regimen, the finger must be allowed to reciprocate between a flexed and an extended position, with the degree of flexion and extension increasing in the course of the regimen. Because the patient has an active role in the post-operative period, the design of the splint should be simple enough to encourage patient participation. The splint should also be as unobstructive as possible, and light enough to prevent fatigue.
In most prior art hand splints, the dynamic force required for finger extension is generated by springs or rubber bands attached to rigging which operates in conjunction with a dorsal outrigger structure. Such splints suffer from several serious drawbacks. Custom fabrication and fitting of outrigger splints is time-consuming (typically 4-8 hours per splint) and requires professional expertise. Moreover, such splints lose accuracy of fit due to exaggerated ulnar directed extension lift and cause resistance to flexion.
Several hand splints are the subject of granted patents. U.S. Pat. No. 4,602,620 discloses an outrigger splint with pulleys juxta-positioned to the fingers of the hand, mounted to the outrigger structure, and guiding a rigging line attached to a fixed-length spring. The dynamic force is controlled by the choice of a colour-coded spring used to anchor the rigging line.
U.S. Pat. No. 4,765,320 discloses an outrigger splint with an elongated, laterally adjustable rigging guide operating as a pulley for changing the direction and the force applied by a rigging. The dynamic force is controlled by an elastic band used to anchor the rigging line.
U.S. Pat. No. 4,949,711 discloses an outrigger splint which uses a single extensible coil spring to generate variable tension force in the rigging. The tension force is adjusted by the choice of attachment point for the coil spring securable on the base of the splint by use of releasable hook and loop fasteners.
U.S. Pat. No. 4,772,012 discloses a dynamic splint with a work arm tensioned by a torsion spring, and a band connected at one end to the work arm and at the other to a connecting member on the finger.
In all of these prior art examples, the dynamic force always pulls the fingers toward an extension position. Some devices allow control of the amount of the dynamic force exerted, either by interchanging the flexible elements which create the force, or by altering their anchorage position. No means is provided for training the fingers in a flexion or partial flexion position or ensuring that the joint will flex relative to a natural pivot axis.
The need has therefore arisen for a dynamic hand splint which overcomes the various shortcomings of the prior art. The applicant's splint described herein is pre-assembled for easier and faster fitting, is readily adjustable while being worn by the patient for optimum joint alignment, and does not apply radial or protractive/retractive forces to the joint during function which can interfere with post-operative tissue healing.